600 



THE BIOLOGY OF MARINE ANIMALS 



longer apparent, and the thorax becomes enveloped by enormous oosteg- 

 ites bounding an incubation chamber. The males are dwarf animals retain- 

 ing the metameric appearance of isopods and are found in the incubation 

 chamber of the female. When the female parasite reaches maturity, an 

 opening is formed through the body wall of the host and larvae are dis- 

 charged to the exterior through this opening (103). 



Sex determination in these animals shows certain interesting features 



8 hp 6 



Fig. 14.11. Diagram Summarizing the Life Cycle of the 

 Entoniscid Parasite Port union maenadis. (From Veillet (103).) 



1 : epicaridium larva, just before hatching; 2: epicaridium larva attached to a copepod 

 Acartia; 3: microniscus stage, fixed on a copepod; 4: free cryptoniscus stage; 5: imma- 

 ture male in a host Carcinus; 6: adult male; 7, 8, 9: stages in the development of a 

 female in a host crab. 



which have been partially unravelled (Fig. 14.12). In the bopyrids a 

 cryptoniscus larva which reaches a host transforms into a new larval form 

 characterized by loss of pleopods. Further development of the male is 

 arrested at this stage, while the females continue to increase in size and 

 become equipped with plate-like respiratory pleopods. Experimentally it 

 has been shown, however, that when young male parasites are removed 

 from the female and placed in the branchial cavity of non-parasitized 

 hosts, the majority develop into normal females. Among cryptoniscids, 

 the cryptoniscus larva which fixes itself upon its definitive host becomes 



